Most girls by the time they reach high school are swinging a 33 drop ten. Power hitters maybe a 34 drop ten or a 33 drop 9. A 31 drop 11 is really small unless your daughter is also really small. It’s what I could consider a 12u bat size. I’d tend to agree with her coaches, she should be using (and should be strong enough to use) the 32, unless she’s very petite. And even then that’s still a smaller bat than most her age are using.